A zoom lens of a rear focus type is known (see Japanese Patent Laid-Open Publication No. 7-151967, which is a counterpart of Japanese Patent No. 3109342). This kind of the zoom lens has a five-group structure in which positive, negative, positive, positive and positive lens groups are disposed in this order from a subject side. The negative second lens group is moved toward an image side when magnification is changed from a wide-angle end to a telephoto end. The fourth lens group is moved to perform focusing and to correct image plane variation caused due to zooming. The first, third and fifth lens groups are securely fixed, so that the entire length of the lens groups is kept constant at the time of zooming and focusing. Moreover, a high zoom ratio of ten times is set and aberration fluctuation is restrained over the entire zoom range to achieve a high image-forming performance.
With respect to the zoom lens having a high zoom ratio, a blur of a shooting image is remarkably caused by camera shake and vibration of a vehicle or the like at a time of a telephoto operation. In view of this, a zoom lens having a vibration-proof function is known (see Japanese Patent Laid-Open Publication No. 7-128619, which is a counterpart of Japanese Patent No. 3359131). In this kind of the zoom lens, a certain lens is moved in a plane perpendicular to an optical axis when vibration occurs. By virtue of this, an image-forming position is moved in a direction perpendicular to the optical axis so that the blur of the shooting image is resolved.
The zoom lens described in the above-noted Publication No. 7-151967 is successful in preventing the aberration from fluctuating at the time of zooming. However, large eccentric aberration occurs when the certain lens is moved in the direction perpendicular to the optical axis. Thus, there is a problem in that the zoom lens of the Publication No. 7-151967 does not have a lens structure suitable for conferring the vibration-proof function.